Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$193.92	11.326%	$215.8834	$215.88	$215.90	$215.90
Purchase #2	$6.87	6.298%	$7.3027	$7.30	$7.30	$7.30
Purchase #3	$37.81	11.453%	$42.1404	$42.14	$42.15	$42.10
Purchase #4	$96.84	8.473%	$105.0453	$105.05	$105.05	$105.00
Purchase #5	$137.59	10.347%	$151.8264	$151.83	$151.85	$151.80
Purchase #6	$143.71	5.548%	$151.683	$151.68	$151.70	$151.70
Purchase #7	$17.61	9.493%	$19.2817	$19.28	$19.30	$19.30
7 purchase totals =	$634.35		$693.1629	$693.16	$693.25	$693.10